Oil is pumped from the ground utilizing a number of different techniques. Included among these is the utilization of sucker rods for lifting oil to the surface; and electrically powered submersible pumps placed down hole for pumping oil to the surface. To facilitate pumping of oil to the surface, flush water is introduced to the oil well. This flush water is then pumped or sucked to the surface as produced water. The produced water includes the desired oil.
The down hole environment is particularly inhospitable to oil production equipment. The equipment utilized is typically subject to corrosion and scale formation. Sometimes, the scale formation can be crippling to the equipment requiring frequent cleaning and replacement. Typically, scale such as formed by Barium sulfate, and calcium sulfate, or calcium carbonate is encountered. Corrosion is also a problem.
Compositions have been prepared which are useful in controlling such scale. One such composition is disclosed in U.S. Pat. No. 3,880,765 issued to Watson. Watson teaches that low molecular weight ethoxylated acrylic polymers are particularly good Calcium (sulfate or carbonate) and Barium sulfate scale inhibitors and tend to remain in solution in the presence of large quantities of calcium salts.
We have found that certan hydroxyethylacrylate/acrylate copolymers are useful in controlling calcium scale.
However, we have recently encountered wells in which zinc sulfide scale formation is a problem. To the best of our knowledge, no art exists discussing the control of such scale. It would be advantageous to reduce or eliminate such scale to facilitate oil recovery.